1. Field of the Invention
The present invention relates to a pattern processing device, a pattern processing method, and a pattern processing program.
2. Description of the Related Art
An image to be projected onto a screen from a projector usually has trapezoidal distortion due to relative positional relation between the projector and the screen. Non-linear distortion due to local irregularities and torsion of the screen onto which the image is to be projected is observed in some cases.
Japanese Patent Application Laid-open No. 2010-028411 discloses the following technique in order to correct the above-mentioned distortion. That is, disclosed is a technique of image-capturing a screen onto which a calibration pattern image formed by a specific figure array has been projected with a digital camera or the like, calculating the degree of distortion from deviation between an ideal position and an actual extracted position of a characteristic point that is extracted on the captured image based on the figure array, and projecting an image corrected so as to eliminate the calculated distortion from a projector.
It is desirable that operations relating to the projection and image capturing of the calibration image be performed with time and effort as less as possible. In spite of this, in Japanese Patent Application Laid-open No. 2010-028411, since the captured image is binarized by a uniform fixed threshold, an appropriate binarization result cannot be obtained if there is local illumination unevenness resulting from states of an indoor illumination and a screen surface. Because of this, the characteristic point fails to be extracted in some cases. If the indoor illumination is turned off during the calibration operation only or image capturing is repeated until the characteristic point is extracted successfully, time and effort are required.
In view of the above, there is a need to provide a pattern processing device that makes it possible to calibrate distortion with a small effort and extract characteristic points with high accuracy even if there is unevenness at the time of projection.